JP2005-076673A, published by the Japan Patent Office in 2005, proposes speed ratio control of a vehicle in which travel motive power is obtained from an internal combustion engine via an automatic transmission, for the purpose of improving re-acceleration performance during uphill travel.
In this prior art speed ratio control, an engine rotation speed lower limit value Nemin for generating a necessary engine output power with an engine torque when the accelerator is fully opened is determined. A speed ratio of the automatic transmission is then controlled so that the actual engine rotation speed does not fall below the engine rotation speed lower limit value Nemin. As a result, the speed ratio is restricted to a low-side speed ratio region, and the re-acceleration performance of the vehicle after passing a curve while traveling uphill is improved.